DE60307580T2 - Improvements in or relating to the production of fiber composites - Google Patents

Abstract

A fibrous reinforcement assembly with a mixture of a liquid resin and a curing agent for the resin. The fibrous reinforcement assembly further comprises a physiochemical immobilisation means (110) disposed at one or more locations on and/or within the fibrous reinforcement. The immobilisation means is configured to impart the localised immobilisation of the liquid resin in the vicinity of the immobilisation means. <IMAGE>

Description

The The present invention relates to improvements in fiber reinforced composites or in connection with the preparation of fiber-reinforced composites.

Fiber reinforced composites are widely used to structures and components for use in a number of different industries, for example Aviation, transportation, electronics, construction and leisure industry.

A common one Approach for the preparation of such structures or components, in particular large components or structures, such as boat hulls, wind turbine blades or certain aircraft components, require the placement of a fiber reinforcement unit within a mold followed by impregnation or infusion of the Construction with a mixture of one or more liquid resins with one or more Curing agents. Once the impregnation or infusing the liquid resin / curing agent mixture In the construction is complete, the liquid resin is cured to the final shaped structure or the final one to give molded component, typically by heating the Construction.

It There are a number of different techniques by which a resin / curing agent mixture in the fibrous reinforcement construction infused or impregnated can be. conventional Techniques involve either brushing or measuring the resin / curing agent mixture on the fibrous reinforcement. Although such techniques in practice are simple and relatively inexpensive to implement are, the resulting product may vary in quality be, and the mechanical properties of the final structure or the component can often be inferior.

Recently Liquid resin infusion technologies, the according to the state technology under various acronyms, such as RTM, VaRTM, SCRIMP, RIFT, etc. are developed. All these techniques are based on the basic concept of injecting or infusing Resin into a fibrous reinforcement unit, either in a closed form in the case of an RTM process or in a vacuum bag forming in the case of a VaRTM or SCRIMP Process. The processes offer due to the improved hygiene and Security with which these mainly closed processes accomplished can be Great mechanical properties of the final composite structure or the final one Composite component and cheaper Manufacturing costs numerous advantages compared to the conventional ones Techniques.

At the Prepare fiber reinforced Components through a liquid resin infusion process It was observed that a tendency of the liquid resin that is in the fibrous amplification unit infused exists in certain areas of the unit while infusing and hardening deplete. This phenomenon is especially common when A vacuum resin infusion process is used to make large components such as wind turbine blades or boat hulls and / or if the liquid resin, that into the fibrous reinforcement unit is infused, has a particularly low viscosity (because low viscosities for Example of special advantages with regard to the rate of infusion Offer). The occurrence of resin depletion can be particularly detrimental, because the final one Structure or the final component, after curing molded of liquid resin not, originally intended distribution of the resin in its entire structure. The mechanical properties and the performance of the structure or the Components thus formed can thus be compromised especially in areas where the resin depletion is occured. The occurrence of resin depletion can often be due to the presence of white Spots on the surface glass reinforced Components are visualized. These can occur during infusion or only after curing become visible.

In In the case of a VaRTM process, for example, the ranges include the unit, whose particular vulnerability for the Occurrence of resin depletion was observed, the areas in nearby the suction piping connecting the vacuum pump to the mold where the resin depletion tends to, as a result of the suction power occur, which is generated by the vacuum pump, and areas, which are in contact with vertically inclined sections of the mold, at which the resin depletion also as a result of gravity effects can result. The resin depletion in these areas occurs in particular with probability, as soon as all spaces between fibers and fiber reinforcement are completely with the infused liquid resin saturated are. Furthermore, the support pressure, which is applied to the unit by the vacuum bag, typically less than 1 bar (100 kPa), which is insufficient as such to avoid the liquid resin from vertically inclined sections of the composition under the Gravity flows out.

Further, when the resin is an epoxy resin, the problem is emphasized when the unit is heated to cause the resin to harden, because the viscosity of epoxy resins significantly decreases during the curing cycle. Although similar to other resin systems, liquid epoxy resins are less likely to harm this sin Viscosity can counteract the viscosity by a rapid gelling hardening mechanism. The temporary uncontrolled reduction in viscosity, particularly when coupled with the fact that it is often necessary to maintain the vacuum suction on the unit once the resin infusion is complete and also during the curing cycle, increases the tendency for resin depletion even more in sensitive areas.

One Approach to solving This problem is a very fast cure system to use; the gel time for Formulated epoxy resin infusion systems can last for only a few minutes and in some cases even less. This can be serious on the viscosity the composition during of the infusion process and on the safety of the process, because of such high reactivity is often accompanied by the generation of high exothermic heat.

It is therefore an object of the present invention, a method and a composition for preparing a fiber reinforced composite structure or a fiber reinforced composite component to provide by a resin infusion process in which the depletion of the Resin in areas prone to resin depletion, significantly is reduced or completely eliminated.

lb ( "Resin Infusion in the US Marine Industry ", Reinforced Plastics (1994), Vol. 38, No. 12, pages 32-34) has a resin transfer molding and grading method with vacuum support (VaRTM-PLP), infusion method according to the preambles of claims 1 or 10, under light curing of a resin infused laminate. The hardened section the laminate can be stopped or started at any point, by sequentially masking the laminate during infusion.

According to one A first aspect of the present invention and as defined in claim 1 becomes a fibrous reinforcement unit provided with a mixture of a liquid resin and a curing agent for the Resin impregnated is, wherein the fibrous reinforcing unit further comprising fixing means, which at one or more locations and / or within the fibrous reinforcement are arranged, wherein the fixing means that the configuration such is that local fixation of the liquid resin near the fixative is awarded.

Preferably the fixing agent is a physical-chemical agent through which the viscosity of the liquid resin can be increased. The physicochemical fixative may be the addition of a Having additive with an intrinsic viscosity-improving feature, such as a thickener or thixotropic substances or alternatively adding an accelerating agent with the liquid resin / Aushärtmittelgemisch reacts to form a gel. The increase in viscosity, which in the liquid resin can be used either to create a region of the liquid resin to fix within the unit, or to create a barrier, around the flow of the liquid resin from a specified zone of the unit to prevent or at least to hinder.

One preferred physico-chemical fixative was claimed 12 defined.

According to one Second aspect of the present invention is a method for Prepare a fiber-reinforced Composite structure or a fiber reinforced composite component as defined in claim 18.

The Problem of resin depletion, its occurrence following the Prepare a fiber-reinforced Composite structure or a fiber reinforced composite component observed with resin infusion process, can by the present Invention solved be by placing the fixative selectively in the areas of the unit is positioned, which tend to resin depletion (that is in vertical inclined sections of the mold or in a VaRTM method for Example in the areas surrounding the vacuum piping), where forming a final one cured Structure or a component allows which is a substantially uniform distribution of resin in has his / her whole structure. It is clear that local fixation of the liquid resin near the fixer of the tendency of the resin from these areas too flow, prevent or substantially hinder them, be it by gravity or by any other driving force.

In addition to providing a solution to the problem of resin depletion, there may also be instances in which controllable local fixation of the resin can be used to achieve other desirable effects, such as closing or blocking a draft tube connection between the vacuum pump and the mold assembly in a VaRTM as well as in a SCRIMP process. This effect could be desirable to facilitate the controlled infusion of resin into the unit, and could be achieved by placing a fixative near the opening of a vacuum suction tube so that when the resin reaches the fixative and local fixation of the infused Resin is added, the suction pipe is effectively closed or blocked. This effect could be used to sequentially close a number of different suction tubes while the liquid resin gradually infuses into various regions of the unit, thus allowing the vacuum suction to be gradually concentrated in the remaining areas of the unit in which complete infusion has not yet been achieved ,

Known Method by which the local fixing of a liquid resin within the unit by the direction of heat to local areas a carrier composition could be realized thereby curing of the resin promoted at this point are described in Butler et al., Proc. Int. Conf. Compos. Mater, 10th (1995), Vol. 3, 269-276 and Shull et al., Proceedings of SPIE, The International Society for Optical Engineering (2000), 3993, 19-22, described. In such processes, however, it is possible to that the heat transfer the curing of the resin over promoting the desirable areas. If for example that Resin system as highly reactive is formulated, that is, if a quick cure is desirable at low temperatures, there is the possibility to promote the curing reaction via exothermic Gain. If no action be taken to limit this, it is possible that curing of the resin over larger areas the composition is promoted, especially in thick sections of the unit. On the other hand, based certain compositions and processes of the invention described herein not on strong reaction chemistry, for the local fixation of resin so that the problem of unwanted exothermic amplification is eliminated.

at In the present invention, the term "fixing agent" means a means for imparting the local fixation of the liquid resin, that into the fibrous reinforcement unit infused by a physicochemical means which is the viscosity of the liquid resin can be increased.

It is particularly preferred that the fixing agent is a chemical Is means by which the viscosity of the liquid resin by the reaction of a so-called "accelerator" with the infused Liquid resin / hardener mixture is increased. This reaction increases the viscosity by the local gelling of the liquid resin causes and thereby prevents the liquid resin flowing freely in the area, in which the chemical agent is applied, and therefore used can be used to prevent the occurrence of resin accumulation.

The Reaction of the liquid resin / hardener mixture with the accelerator does not necessarily give the full curing of the Resin nearby of the fixing agent. It is only necessary that the viscosity of the liquid resin increased to one measure is sufficient to prevent its flow and therefore be deprived from close by of the chemical agent. Full curing of the fixed area can by continued reaction between the resin and the curing agent occur, often at elevated levels Temperature. Alternatively, the accelerator used in this Range is also applied to this continued reaction be involved.

The Accelerator can either be directly on the surface of the fibrous reinforcement unit applied and / or impregnated in these or, if this unit consists of a number of leaves or Layers of a fiber-reinforced Material consists of the accelerator may be to some or all of these individual leaves or layers are applied and / or impregnated into them. The latter Application form is particularly desirable if a comprehensive Fix the liquid resin through the whole unit is desired at a given location.

While that Liquid resin / curing into the fibrous reinforcement unit penetrates the accelerator in the surrounding area be dispersed. If that is the case, it is believed that the Use of accelerator in units of the unit at would be most appropriate in which the resin flow rate through the unit during of the infusion process is low. In practice are most areas of the unit that tend to resin depletion and in which the fixation of the liquid resin is therefore desirable is to the periphery of the unit, where the unit is typically thinner and the resin flow rate typically lower. In these areas, therefore, the dispersing and diluting of the accelerator in the surrounding area by the flow of the Infusionsharz- / Hardener mixture restricted.

Preferably occurs the local reaction between the accelerator and the liquid resin / curing agent mixture at a time near the end of the resin infusion, when the Flow rate low is.

In in the case of the SCRIMP process, where the rapid flow of the Liquid resin / Aushärtmittelgemischs over the surface the lower surface the unit favors is penetrated, before being penetrated against the mold surface, that could Accelerator preferably at a number of layers over the Strength the fibrous reinforcement unit and not just on the surface be applied to the unit.

In In the case of VaRTM processes, the accelerator can be applied to the fibrous reinforcement before draining the unit and infusing the fibrous reinforcement with the liquid resin / Aushärtmittelgemisch be applied.

Although a mere application of the accelerating agent to the fibrous reinforcing unit is generally preferred, some additional components may be included in the accelerator to assist in fixing the accelerator within and / or on the surface of the fibrous reinforcement. An example of such additional component that may be used is a thixotropic material such as fumed silica, available from Cabot Corporation under the trademark Cabosil ^® or from Degussa Ltd. under the trademark Aerosil ^®.

If attaching pure accelerator at any point give a local accelerant concentration that is too high can, the accelerating agent can be dissolved in a solvent, that later is rinsed off. Importantly, every carrier solvent is completely eliminated, and this can be done using heat and / or Vacuum processes take place. The skilled person understands that such Technology during a vacuum resin infusion process by draining the unit can be done before the resin infusion, if the accelerator as a solution supplied becomes. Furthermore, the feeding a solution of the accelerator, the application of the accelerator on the fibrous reinforcement by a corresponding spray or To facilitate painting by the form technician. It can be too for the Carrier solvent be suitable to be eliminated as described above by relies on the use of the vacuum, which is usually associated with pulling liquid resin into the unit becomes. However, you have to all restrictions, by the activity of the accelerator are taken into account.

It however, it is preferred that the accelerator be applied to the fibrous amplification unit in the form of a so-called "accelerator carrier" is applied. With "accelerator carrier" is a piece or a strip of a suitable carrier substrate meant, which is impregnated with the accelerating agent.

The "accelerator carrier" can be separated as pieces or strips of the carrier substrate be preimpregnated with the accelerator. According to one Another aspect of the present invention therefore provides an "accelerator carrier". on and / or in a fibrous reinforcement unit comprising a carrier substrate having an accelerator as defined herein waterproof is, can be arranged.

The use of an "accelerator carrier" is particularly advantageous because it obviates the need for the form technician to directly handle the accelerator As for applying the accelerator directly to the fibrous reinforcement unit as discussed above, it is preferred that the carrier substrate be alone with the accelerator is impregnated, but it may be necessary in some cases to add additional components (e.g. Cabosil ^®) to support the fixing of the reagent either within or on the surface of the carrier substrate.

It can be any suitable carrier substrate for preparing an "accelerator carrier". Suitable examples include textiles, especially light fabrics and rough tissue of natural or synthetic fibers, such as nylon, polyester, cotton fiberglass or Carbon fiber in quilted, knitted, woven or mat shapes. The carrier substrate of the "accelerator carrier" could therefore be either the same material as the fibrous reinforcement unit or different. In most cases becomes an "accelerator carrier" on thin sections applied to the fibrous reinforcement. In such cases can a sufficient amount of the accelerator on a lightweight fabric material impregnated be such as the quilted fabrics or straps that often used in the adhesive technique. This very light impregnated Articles are particularly suitable for inclusion in one soaked Wind turbine blade reinforcing agent or a boat hull because its effect on the performance of the final component probably negligible is. The "accelerator carrier" can be applied to the surface of the fibrous reinforcement or alternatively, if the fibrous reinforcement consists of a number of Layers or leaves of reinforcing material exists, applied between some or all of these layers or leaves become. The latter form of application is particularly desirable, if a comprehensive fixation of the resin through the whole strength of the fibrous reinforcement unit is required. In some cases It may be preferable to use the "accelerator carrier" between each Scroll or Layers of fibrous reinforcement be staggered, so that a gradual and controlled Increase the viscosity of the resin is lent while the resin is infused through the unit. This is particularly desirable in thick sections of the unit in which the resin flow is likely is high.

The Accelerator could on the carrier substrate of the "accelerator carrier" in a solvent as above in connection with the application of the accelerating agent directly on the fibrous reinforcement unit be discussed, be applied. In such cases, the solvent could impregnate and remove the subsequent solvent Be part of the manufacturing process of the "accelerator carrier".

The carrier substrate can be attached to the fibrous reinforcement unit secured using a small stitch or knot of fiberglass be similar in a way the one at which the different layers of the fibrous reinforcement unit typically secured to each other. Experimentation determines that optimal positioning of these pieces for every Application, both in the level x-y (in the level of reinforcement) as also in the plane z (by the unit). The exact positioning is probably for every reinforcement unique.

Preferably the "accelerator carrier" is easily recognizable colored to distinguish it from the rest of the fibrous reinforcement except when the aesthetic Appearance is important, and he therefore the same color (or no Color) like the rest of the fiber reinforcement can have. In the previous one In this case, a shade of red becomes particularly suitable for adequately promoting the enhanced reactivity of this special part of the unit.

While that Resin into the fibrous reinforcement unit penetrates and meets the accelerator, the curing process accelerated, and the viscosity of the liquid resin rises much faster than in other areas, where no accelerator currently is. Depending on the exact nature of the selected accelerator Heat can be developed rapidly, and appropriate allowance should for this possibility be provided as needed. However, as the main application of this Accelerator primarily in thin vertical sections the fibrous reinforcement unit in which the resin depletion tends to occur the most, the reaction enthalpy should be distributed quickly and only a few Raise problems. However, significant heat conduction can also the curing promote the non-accelerated region of the adjacent resin, as described above, which may or may not be desirable.

• (i) unter Vakuum nicht flüchtig,
• (ii) schnelles und einfaches Mischen mit dem Flüssigharz-/Aushärtmittelgemisch,
• (iii) Kompatibilität mit dem Aushärten des Infusionsharz-/Aushärtmittelsystems,
• (iv) leichtes Lokalisieren auf der faserigen Verstärkung und
• (v) Fördern des schnellen und effizienten Aushärtens des Infusionsharzsystems.

The selected accelerating agent, whether for direct application to the fibrous reinforcing unit or for preimpregnating onto or into an "accelerator carrier", will depend on the specific resin / curing agent mixture present in the composition Any suitable accelerator could be used to trigger the local gellation of the liquid resin The main criteria which such accelerators should preferably meet are:

• (i) non-volatile under vacuum,
• (ii) quick and easy mixing with the liquid resin / curing agent mixture,
• (iii) compatibility with the curing of the infusion resin / curing agent system,
• (iv) easy localization on the fibrous reinforcement and
• (v) promote the rapid and efficient curing of the infusion resin system.

In some cases, it is preferable that the resin is an epoxy resin that is mixed with an amine curing agent, and in these cases, the accelerator may be a reagent that reacts with either the amine curing agent and / or the epoxy resin to accelerate or cure to let progress. Typical accelerators that could be used to cause local gelling of an epoxy resin / amine curing agent mixture are inorganic salts of various metals. Suitable examples of such salts include those in US 4,668,736 . US 5,198,146 . US 5,958,593 . US 4,101,459 and US 5,442,035 described herein, the entire contents of which are hereby incorporated by reference. These are known accelerators for the amine curing of epoxy resins.

Merkaptanverbindungen, such as the series Capcure ^® could also be used as an accelerator. Merkaptanverbindungen react very easily with epoxy resins and cure them quickly, especially in the presence of tertiary amine curing agent.

The accelerating agent may also be an agent which gives a Michael addition reaction with the amine curing agent to form an adduct which then reacts with the epoxy resin to form a highly crosslinked resin matrix. Such accelerator is dipentaerythritol (Sartomer ^® 399). ^® Sartomer 399 is particularly recommended for the Acrylatpolymerisieren via the 5-unsaturated residues on the molecule. Its ability to undergo a Michael addition reaction with amine curing agents has also been reported. The reaction between Sartomer ^® 399 and the resin / Aminaushärtmittelgemisch resulting initially in the formation of a rubbery gel. In this form, the epoxy resin is effectively immobile in reinforcement, but retains the ability to undergo amine cure, either through another reaction in a similar manner, or through the curing mechanism that accounts for the majority of Resin infusion is designed.

A disadvantage associated with the use of Sartomer ^® 399 is in its potential to show an uncontrollable free-radical polymerization reaction. To reduce the chances of this happening, inhibitors may be included in the composition. Since the Michael addition reaction, not due to Sartomer ^® 399, which is used in the present invention to such free radical chemistry, the activity and the loading of free radical inhibitors could be strengthened to reduce the risk of the occurrence of free radical To further eliminate polymerization reaction and thereby increase the applicability and safety of this process.

The Appearance of resin depletion observed with liquid epoxy resins is not the case with resin systems with free-radical curing very a problem like the unsaturated one Polyester resins because these resin systems are different than the epoxy resins easy to gel in a predetermined time after infusing can be modified. The allows the rapid onset of gelling by the time in which the resin infusion is complete and prior to promoting full heat set. The requires a well-thought-out selection of initiators, retarders and Inhibitors, which the person skilled in the art knows how to carry out. It can, however, still Give cases in which the controllable, local gelling of the free radical cured resin is still required. An example of such a case would be the one above mentioned application, in which the local gelling of the liquid resin could be used to close the suction, the is applied by vacuum as soon as the unit or one of its Areas fully infused with the resin.

The Gelling of the free-radical resin systems is by and large Heat mediates and could Therefore, be triggered by local heating of the composition. additional Components, such as inhibitors, are usually in of the composition to modify the reaction profile and gelling the resin by preferentially reacting with the resin triggering element to delay. Only when these inhibitors are used up, the fast Really "go through" polymerization reaction, and the addition polymerization reaction promotes then the quick Harzgelieren. Suitable combinations of components to realize this effect are well known to those skilled in the art.

The fast production of the trigger element can also be different from heat be effected. In certain embodiments of the invention could forming highly reactive radical elements simply over the Promoted use of catalysts become. these can either act as true catalysts, with very small proportions work well, even in the solid phase, or as part of one Reduction-oxidation pair (redox). Certain embodiments the invention could that Locating a half a redox pair on one "accelerator carrier" and the other half in the resin / curing agent mixture exhibit. While the polyester resin is infused into the unit, the mutual action between the two halves of the redox couple the fast Harden of the present unsaturated Elements begin. This reaction is enough to at least locally the Overcome the effects of inhibitors in the formula. Certain metal ions could also used to break down the free-radical initiators to catalyze, and low concentrations of suitable metal salts could on the "accelerator carrier" isolated or alternatively applied directly to or in the fibrous reinforcement itself. It is predicted that the free-radical initiators, the catalyzed fragmentation subject, even under normal heat release would work, only the reaction is running under normal heat release with a much more controllable rate. In essence, the Task is to promote a level of "uncontrolled" reaction of the "accelerator carrier" location. Everyone these approaches for the local catalytic triggers the polymerization could independently from the main reaction chemistry.

The Accelerator, whether it is now pure on the fibrous reinforcement unit coated or positioned within the unit in the form of a prepreg "accelerator carrier", Can be easily selected Areas of the unit are applied in which the local fixation of the infused liquid resin is required. It is clear that selective positioning of the accelerator, the pattern of precure gelling, that results, prescribes. The pattern of gelling required depends on every specific application. In some cases it may be advantageous, for example so be a precure gel pattern organize that free channels remain unfixed resin, by the residual air or volatile by-products can be removed from the system. This reduces the likelihood of trapping gaseous elements the porosity contribute to the laminate and therefore a reduction in the quality of the final structure or component.

In some cases, it is also advantageous to leave channels of unfixed liquid resin within the unit to allow the liquid resin to flow past the gelled resin and / or over the top thereof. With such anord It is more difficult for the liquid resin to flow back through the composition once the infusion is complete, so that the liquid resin is retained within the desired range of composition and thus allowed to cure normally.

Further The accelerator may also adhere to the fibrous reinforcement in Form one or more lines of accelerant that directly on the fibrous reinforcement applied, or as one or more Strip of a preimpregnated "accelerator carrier" on the unit be attached so that when the liquid resin with the accelerating agent in touch comes, a reaction between the accelerator and the resin / Aushärtmittelgemisch entering and forming a barrier of gelled resin, which may be configured to keep the flow of adjacent areas of the liquid resin from the selected one To prevent or at least hinder the area of unity. at This arrangement effectively "grows" the barrier from the liquid resin, while the reaction with the accelerating agent takes place.

alternative could special forms of the "accelerator carrier" piece are used, to form gelled or cured resin "pockets" through the unit to promote, what could be used to effectively catch resin and thus flow out a selected zone to prevent under gravity.

Preferably should follow the infusion and the final curing of the resin the final one Composite component or the structure does not differ from the which was prepared without local acceleration except the obviously improved quality in the areas that too Resin removal tend to be where the liquid resin is within the unit was fixed.

The Amount of accelerator applied to the fibrous reinforcement must be sufficient, either directly or pre-impregnated within an "accelerator carrier", for the local fixation of the liquid resin to lend in the unit. In some cases, the required Batch high (> 10% Mass fraction), and if that's the case, that works Accelerator is best where the resin flow rate is within the unit is low. In areas where the flow rate is high is, the accelerator may be purged through the unit and from the resin diluted as discussed above become. This may be the resulting increase in the viscosity of the liquid resin, which occurs, decreases, and also locates resin fixation reduce. To account for this phenomenon, could be different Batches of an accelerator to different areas of the Unit applied to the different flow rates too consider, or, alternatively, "accelerator carrier" pieces could be used with different accelerator charges for fixing the liquid resin at different flow rates to get prepared. For example, an "accelerator carrier" piece or Strips a high charge of accelerant for areas containing a fast resin flow and a lower charge of Composition for Areas of slow resin flow. Alternatively, a more reactive accelerator could be used be arranged in areas where the flow of the resin is fast and an accelerator with lower reactivity could be present Areas are used in which the resin flow is slow.

One Advantage of Mediating Local Fixation of the Liquid Resin by causing gelling of the resin by the reaction with An accelerating agent is that during the curing cycle, in which the resin composition is initially heated, the viscosity of the gelled areas of the resin remains high, causing the flow of the resin from the gelled Prevented areas or at least significantly reduced becomes. This feature is particularly important when the liquid resin, which is infused into the unit is an epoxy resin, in which an initial one Reduction of viscosity while the heating of the resin for curing may occur, and the subsequent increase the viscosity, while the curing takes place is ordinary much slower than the "pseudo-command hardening" possible with free-radical systems. In the absence of an accelerator, reducing the viscosity overcomes raising the temperature is causing it, at least for a while any increase in viscosity due to the progress of the resin and continuation of the curing. During this Part of the process are the problems of unwanted resin flow (against which protect the invention should) be the most acute. Usually will Insulating materials used to infuse the unit during the curing and, if so, the occurrence of the Resin removal possibly only during molding of the final cured component or the structure. The problem is also caused by the use of one Resin system with low viscosity worse, which of a number of operators of rapid infusion systems preferred becomes.

It is also clear that for operators using a vacuum resin infusion process, it is normal to moderate the level of vacuum applied to the unit in order to adapt it to each stage of the manufacturing process. A high vacuum is therefore used while the urine ur is initially sucked into the reinforcement, and a lower vacuum is used when the unit is fully filled. Maintaining a low vacuum is important during curing to avoid the occurrence of porosity in the layered product resulting from volatile die components, released air, or volatile reaction products. The constant application of at least one light vacuum helps consolidate the structure and realize the correct resin / reinforcement ratio. By maintaining the vacuum, the flow of low viscosity resin within the unit is further enhanced.

It Furthermore, it often turns out to be difficult, a uniform heat distribution at large Molds, such as a wind turbine blade shape. That can cause that longer curing times are required while Areas that are difficult to heat to the required temperature to be brought. Another advantage of fixing the resin through Gelling in such circumstances is therefore effectively giving these areas a head start although it does not quite replace the requirement of posthardening. The skillful arranging such fixative can therefore the requirement providing significant additional heating during the curing cycle bypass.

at a further alternative embodiment of the invention the chemical fixative, by which the viscosity of the liquid resin being raised, adding a viscosity-enhancing Material in the form of extra resin that serves the local viscosity of the liquid resin, the in a selected one Infused area, increase. The extra resin preferably has a higher viscosity than that Main resin and may be partially cross-linked (B-stage) or an alternative Resin mold, such as a solid or semi-solid resin mold (for Example solid or semi-solid bisphenol A, where the infusion resin a liquid Bisphenol A is or an epoxide analog or a lower formulation Viscosity). In most cases has the extra Resin a higher Molecular weight and therefore a higher viscosity than that Liquid resin, that for impregnation the main part of the fibrous reinforcement is used. The extra Resin could on the fibrous reinforcement either applied as a paste or as a pure application. In addition, can the resin also applied directly to the fibrous reinforcement unit or on or in one or more leaves of the carrier substrate be impregnated (for example fabric sections or fibrous reinforcement), the following positioned on or within the fibrous reinforcement unit become. Although there are disadvantages, which are that the viscosity-increasing effects are too local (that is on the interlayer layers of fibrous reinforcement alone limited), can be a flush out of the additional Resin occur when the liquid resin / Aushärtmittelgemisch through the fibrous reinforcement infused, and although curing by dissolving of the curing agent in the liquid resin / curing agent mixture be affected This form of fixative is useful in certain applications valuable.

Alternatively, the chemical agent for increasing the viscosity of the liquid resin comprises adding a thickening agent or thixotropic material. Suitable examples of thixotropic agents may be hydrophobic silica (eg, Cabosil ^®), zeolite, clays, short glass fibers or beads. Such materials may be applied to the unit dry or as a paste, although care must be taken to ensure that efficient mixing with the infusion resin occurs.

The liquid resin Can the fibrous reinforcement unit impregnated by any suitable resin infusion or impregnation process or infuse. Preferably, the resin is made by a liquid resin infusion process infused, such as a VaRTM, SCRIMP, RIFT or RTM process.

at the compositions and process of the present invention Can the fibrous reinforcement unit from any of the materials mentioned above as possible carrier substrates of the "accelerator-carrier" unit getting produced.

The Selection of suitable curing agent, the to mix with the resin hangs of the type of resin used, and one skilled in the art will know how to do so Combinations selected become.

Alone for illustration, an embodiment of the present Invention in more detail below with reference to the accompanying Drawing described.

1 Fig. 10 is a schematic illustration of the end portion of a resin infusion layer unit for a large structural member in partial section.

The end portion of the vacuum resin infusion layer unit 101 , in the 1 is shown has a shape 102 for a large structural component, which in this case is a wind turbine blade. In contact with the surface 102 the form 102 there is a fibrous reinforcement unit 103 covered with an impermeable outer leaf 104 is covered to form a dense vacuum bag.

The fibrous reinforcement unit 103 consists of several leaves of starch, which are fastened together. In the main body of the layer unit, that is in the area indicated by the arrow 107 in 1 is an SCRIMP infusion network between the fibrous reinforcement 103 and the impermeable outer sheet 104 positioned.

The vacuum bag is connected to a vacuum pump (not shown), the operation of which results in the evacuation of the vacuum bag (and thus the fibrous reinforcement encapsulated therein 103 ) and causes a liquid resin / curing agent mixture, such as Prime 20 from SP Systems Ltd. (a two-part system with liquid resin and curing agent in which the two ingredients are premixed in the proper ratio just prior to injection / infusion) into the fibrous reinforcement unit 103 from a reservoir (not shown) through the resin inlet tube 105 is sucked. Resin infusion channels (not shown) are provided to allow the resin, the fibrous reinforcement unit 103 to penetrate in a controlled way. In the 1 The layer unit shown is designed so that the resin quickly over the main body area, by the arrow 107 is shown flows, and then slower to the mold surface 102 spreads. The flow in the vertically inclined portions of the layer unit, such as in the area 106 who in 1 is shown, then occurs in the direction of the arrow 108 one.

As soon as infusing with the liquid resin curing agent mixture is complete, the resin is cured to the wind turbine blade section to build.

As discussed above, it has been observed that the liquid resin / curing agent that is infused into the unit tends to flow out of certain areas of the unit before the curing of the resin can be facilitated. The most notable areas in which the occurrence of this phenomenon has been observed are the areas surrounding the vacuum suction tubing connecting the vacuum pump to the unit and the areas of the unit in contact with vertically inclined portions of the mold surface, such as the area 106 in 1 , The area 106 corresponds to the adhesive flange of the wind turbine blade and the occurrence of resin depletion in this part of the blade structure may in particular damage the mechanical properties and the performance of this flange.

Therefore, to prevent the liquid resin / curing agent mixture from flowing out of this region of the layer unit, "accelerator carrier" pieces become 101 . 110b and 110c on and / or within the fibrous reinforcement 103 (as in 1 positioned) prior to infusing the liquid resin / curing agent mixture. These pieces consist of one or more sheets of fabric (or any other suitable fibrous carrier material) impregnated with an accelerating substance capable of reacting with the liquid resin / curing agent mixture to impart local gelling as defined above.

While the liquid resin / Aushärtmittelgemisch in the vertically inclined region 106 the fibrous reinforcement unit 102 infused, it comes in contact with the accelerating substance, and the gelling reaction occurs. This gelling reaction increases the viscosity of the liquid resin / curing agent mixture in the vicinity of the "accelerator carrier" piece which, in turn, prevents or at least minimizes the occurrence of resin depletion from this region by gravity effect, then the resin can be cured normally to form a wind turbine blade. which has a substantially uniform resin distribution throughout its structure, including the adhesive flange.

Claims (22)

Fibrous reinforcement unit ( 103 ) with a mixture of liquid resin and a curing agent for the resin, wherein the fibrous reinforcement unit ( 103 ) further comprising fixing means disposed at one or more locations on and / or within the fibrous reinforcement, characterized in that the fixing agent is a physical-chemical agent by which the viscosity of the liquid resin can be increased, and which is configured to provide localized fixation of the liquid resin in the vicinity of the fixative. Unit ( 103 ) according to claim 1, wherein the unit ( 103 ) comprises a plurality of sheets or layers of the fibrous reinforcing material. Unit ( 103 ) according to claim 1 or claim 2, wherein the physico-chemical agent comprises an accelerator or additional resin of higher viscosity than the liquid resin. Unit ( 103 ) according to claim 3, wherein the accelerating agent is applied to the fibrous reinforcing unit ( 103 ) is applied and / or this is impregnated therewith. Unit ( 103 ) according to claim 3 or claim 4, wherein the liquid resin reacts with the accelerating agent to form a gel. Unit ( 103 ) according to any one of claims 3 to 5, wherein additional ingredients are included in the accelerating agent to modify its physical properties. Unit ( 103 ) according to claim 6, wherein the additional ingredients are selected from thickeners and thixotropic substances. Unit ( 103 ) according to claim 7, wherein the thixotropic substance is selected from hydrophobic silica, zeolites, clays, short glass fibers or spheres. Unit ( 103 ) according to any one of the preceding claims, wherein the resin is an epoxy resin mixed with an amine curing agent. Unit ( 103 ) according to any one of claims 1 to 8, wherein the resin is an unsaturated polyester resin. Unit ( 103 ) according to one of the preceding claims, wherein the localized fixing of the liquid resin defines one or more channels. Accelerator carrier ( 110a . 110b . 110c ) for placement on and / or within a fibrous reinforcement unit ( 103 ) having a support substrate impregnated with an accelerator. Accelerator carrier ( 110a . 110b . 110c ) according to claim 12, wherein the carrier substrate comprises natural or artificial textile material. Accelerator carrier ( 110a . 110b . 110c ) according to claim 12 or claim 13, wherein the carrier substrate is impregnated with undiluted accelerator. Accelerator carrier ( 110a . 110b . 110c ) according to any one of claims 12 to 14, wherein the accelerating agent is applied to the substrate in the form of a solvent solution. Accelerator carrier ( 110a . 110b . 110c ) according to one of claims 12 to 15, wherein the carrier substrate is attached to a fibrous reinforcing unit by fiberglass stitch or knot. Accelerator carrier ( 110a . 110b . 110c ) according to one of claims 12 to 16, wherein the accelerator carrier ( 110a . 110b . 110c ) is colored. A method of preparing a fiber reinforced composite structure or component comprising the steps of: i) applying a fiber reinforced unit ( 103 ) in a form ( 102 ) for the structure or the component, ii) infusion of the fiber-reinforced unit ( 103 with a mixture of liquid resin and a curing agent for the liquid resin, and iii) facilitating the curing of the liquid resin, characterized in that fixing agents are arranged at one or more locations on and / or within the fibrous reinforcement, the fixing agent being a physico-chemical Are means by which the viscosity of the liquid resin can be increased, and are configured to impart the local fixation of the liquid resin in the vicinity of the fixing agent. The method of claim 18, wherein the fixing agent is an accelerator. The method of claim 19, wherein the accelerating agent is applied to the fibrous reinforcing material as a neat accelerator, a solvent solution or an accelerator carrier ( 110a . 110c . 110b ) is applied. Method according to one of claims 18 to 20, wherein a vacuum on the unit ( 103 ) is applied to the resin in the unit ( 103 ) to draw. The method of claim 21, wherein the vacuum is reduced so that the unit is filled with resin.